1. Technical Field of the Invention
The invention relates to resource reservation in a packed switched telecommunications network. In particular, and not by way of limitation, the present invention is directed to a system and method for making efficient resource reservation in an Internet Protocol (IP) network for achieving strict Quality of Service (QoS) requirements controlling traffic in a Universal Mobile Telecommunications Network (UMTS) Terrestrial Radio Access Network (UTRAN).
2. Description of Related Art
UTRAN is the Radio Access Network of 3rd rd generation mobile networks. Efficient bandwidth utilization is an essential problem in UMTS access networks because radio links or narrow leased lines are used in this part of the network. In UTRAN different traffic types having different QoS requirements are delivered in the same time and in the same link. UTRAN is characterized by strict delay requirements and short buffers. In order to meet the strict QoS requirements advanced traffic control methods have to be used. Traffic control usually includes packet scheduling, classification and call admission control (CAC).
Transport technology of UTRAN is based on currently on Asynchronous Transport Method (ATM) and Internet Protocol (IP) as it is described in 3GPP TS 25.401, 3GPP, TSG RAN: UTRAN overall description. As a general tendency, earlier versions of UTRAN are based on ATM while new versions will be based on IP technology. The major motivation to introduce IP technology in UTRAN is that IP allows more flexible fault handling and auto-configuration functions. Besides, it is expected to be a cheaper technology because of the wide deployment of IP routers.
The traffic parameters have to be signaled to UTRAN nodes when a new call is set up. The signaled parameters should be conformed to standard traffic control solutions. The control plane for AAL2/ATM transport network in UTRAN is specified in Q.2630.2 ITU-T recommendation (12/2000): “AAL Type 2 signaling protocol (Capability Set 2)”. The control plane for IP based transport network is under specification in 3GPP.
For ATM based UTRAN an accurate CAC algorithm was developed that calculates the required bandwidth for the configuration of the number of active calls belonging to different traffic classes and for the new call in a link. The CAC algorithm is described in Sz. Malomsoky, S. Racz and Sz. Nadas, “Connection Admission Control in UMTS Radio Access Networks,” Computer Communications, Special Issue on 3G Wireless and Beyond for Comp. Communication, June 2002. It takes into account the activity of the calls and also exploits the periodicity of the traffic at the so-called Iub or Iur interface.
In IP based UTRAN, in order to achieve QoS, different QoS models and provisioning methods are considered such as Integrated Services (IntServ), Differentiated Services (Diffserv), different measurement based methods or over provisioning. These methods have different signaling requirements, which are analyzed in Manner, J. and X. Fu, “Analysis of Existing Quality of Service Signaling Protocols”, draft-ietf-nsis-signalling-analysis-01.txt, February 2003 in more detail.
In IP networks RSVP is the most common resource reservation signaling protocol which is published by R. Braden et. al.: Resource ReSerVation Protocol (RSVP)—Version 1 Functional Specification, RFC 2205, September 1997.
In Next Steps in Signaling (NSIS) working group Internet Engineering Task Force (IETF) a new signaling protocol for providing QoS in IP network is under development. The protocol will be based on RSVP and it will support different QoS models. NSIS protocol aims to meet the requirements of mobile networks and it may be used for transport network control plane in UTRAN in the future.
FIG. 1 shows packet arrival of a periodic ON-OFF like traffic model, where the time is denoted by t, packet size by v, transmission time interval by TTI, time of ON periods by Ton and time of OFF periods by Toff. Ton and Toff define a so-called activity factor measured by A=Ton/(Toff+Ton). In UTRAN the traffic through the Iub or Iur interface can be characterized by a periodic ON-OFF like model as it is described in 3GPP TS 25.401, 3GPP, TSG RAN: UTRAN overall description. The CAC method described in this document checks two different criteria: whether there is congestion due to ON-OFF like behavior and, in a smaller time scale, the probability of the delay violation of the packets are below the required limit. In a link where different traffic types are multiplexed, the delay of packets depends significantly on the queuing and scheduling method used in the system. Priority for the traffic classes having strict delay requirements are applied.
Investigations showed that the delay violation probability monotonously increases with the length of the ON periods, by fixing the activity factor value. Furthermore, considering typical UTRAN delay requirement and transmission time interval TTI values, the delay violation probability only little depends on the length of the ON and OFF periods.
Therefore, as a worst case scenario, infinite ON and OFF periods are assumed in the model and application level call activity is taken into account by using average activity factors characterizing the different connection types.
FIG. 2 depicts another model called token bucket model, which is used to describe and shape bursty traffic of Internet applications presented by J. Wroclawski: “The Use of RSVP with IETF Integrated Services, RFC 2210, September 1997”. A token bucket allows peak rate p for a limited time period, determined by the bucket size b, after which traffic rate cannot exceed the token rate r. The maximum packet size is denoted by M in the figure.
The traffic envelope in these cases is an upper bound of the user traffic. If user traffic is shaped by e. g. a leaky bucket algorithm the traffic envelope is a curve as it shown in FIG. 2. If the traffic is a periodic traffic, the traffic envelope is as it is shown in FIG. 1.
Future NSIS protocol will support standard IP based QoS models like IntServ and DiffServ. IntServ is based on a one-token bucket model. Token bucket traffic descriptors cannot be converted one-by-one to the traffic descriptors of a periodic ON-OFF like traffic model described above.
A one-token bucket model is not suitable to describe periodic ON-OFF like traffic in efficient way. In a one-token bucket model the bucket size should be set to the packet size, the token rate should be set to at least v/TTI, peak rate to v/D in order to conform Iub or Iur traffic where v denotes the packed size, TTI is the time period and D stands for the delay criterion. In this way neither activity of a call (ON-OFF like behaviour) nor the periodic behaviour of Iub or Iur traffic can be taken into account easily in a resource reservation function. This results in that over-dimensioning and over-provisioning is needed and, therefore, link utilization is less efficient.
If infinite ON and OFF periods do not provide a good approximation for a traffic type, the long-time behavior of the traffic sources cannot be characterized by a single activity factor parameter. In this case a more detailed traffic descriptor is needed.
In general, there is no standard solution yet how to describe a periodic ON-OFF like traffic in an IP based resource reservation signaling protocol.
Thus there is a particular need for a new QoS service object proposed for resource reservation signaling protocols that can be used for making efficient resource reservation for a periodic ON-OFF like traffic in a packed switched, especially in an IP based network.